The International Panel on Climate Change (the world’s body of climate scientists - one of the biggest science projects ever) has just released a report into how we can avoid warming the Earth above 1.5 degrees celsius. This 1.5 degrees limit was agreed in Paris as likely to avoid the most severe climate impacts. This is the first in a series of reflections on the report and what it means for climate action.

What should we take away from this week’s report from the world’s scientific authority on climate change, the IPCC, on the implications of the Paris Agreement’s commitment to limit global warming to 1.5C? For some, the temptation will be to dismiss this goal as impossible to achieve. It is certainly difficult not to see it as implausible, based on the analysis presented here on what would be necessary to meet it. The scientists tell us that staying below 1.5C demands, “rapid, far-reaching and unprecedented changes in all aspects of society.” We’ll need to invest around 2.5% of global GDP, around $2.4 trillion, every year for the next few decades. “We all have to fundamentally change the way we live our lives”, says IPCC co-chair Dr Debra Roberts. No biggy then.

On the other hand, the report also makes it crystal clear that the idea that things can carry on broadly as they have in the past is far less plausible than this. The cost of the transformative infrastructure investment needed to hit 1.5 is just a fraction of the projected costs of dealing with the impacts of 2C or more of warming, while there is no meaningful way to put a price on exposure to the much higher risk of truly catastrophic ‘hothouse earth’ scenarios which comes with exceeding 1.5C. No change is not an option. The choice we face is between the implausible challenge of planned and managed disruption through a deliberate transformation of our societies, or the near certainty that chaotic, destructive disruption will be visited on us through forces that we have let slip out of our control. Either way, no aspect of our lives will remain untouched by climate change in the 21st century.

For people asking what this report means for the Paris Agreement itself, the answer is simply self-awareness. Politicians the world over were happy to sign up to an agreement that seemed to signal intent to solve a problem in the future - long after most of the signatories will have left office. What today’s report makes clear is that fulfilling this commitment is not some future problem for future politicians, but a profound and urgent challenge to all societies and governments today, tomorrow and next week. Fulfilling the Paris Agreement is no less plausible today than it was yesterday. Now that we know what we have signed up to, we just have a much clearer view of the terrain ahead, and the meaning of the political choices we confront in navigating that terrain.

It seems unlikely that this moment of collective political epiphany will lead more countries to desert the Paris Agreement as Trump has threatened to do with the US. After all, there is nowhere to desert to. We are very much all in the same planetary boat, and only the most prone to self-delusion are capable of pretending otherwise. As the richest country in the world, the US is in many ways the freest to entertain survivalist fantasies on a much hotter planet, at the same time as having the most to ‘lose’ in accepting the necessity of change today. This road of outright denialism is not open to other countries. As such, the most likely outcome in the immediate aftermath of this IPCC report is more ambition from the already ambitious - and more dissembling and prevarication from the major oil, gas and coal producing economies.

Where do we go from here? The only viable option is to actually start work on rising to this challenge. We are late to the game, but there is still everything to play for. Every ton of carbon kept out of the atmosphere improves our collective chances, so if we shoot for the moon and miss, we may yet land among the stars. It’s not all going to be hard work and sacrifice either - many aspects of rapid decarbonisation will improve lives in other ways too. After all, what’s not to love about planting vast new forests? Ending coal use and driving internal combustion engines out of our cities will clear the air so our kids can breathe. Massively improving energy efficiency means less waste and warmer, more comfortable homes for all. Cycling and walking more and eating less meat will make us healthier. Renewable energy sources like wind and solar have plummeted in cost over recent years, and are now outcompeting fossil energy on cost as well as public popularity. Maybe - just maybe - this isn’t going to be as hard as it looks? We won’t know until we try.

Tackling climate change is the fight of all our lives, despite few people having realised this truth so far. Perhaps after this week there will be more of us.